The invention relates to an apparatus for reducing the water content of water-containing, granular brown coal under the action of thermal energy and pressure on the material distributed in bed form. An apparatus of this type and the process carried out using it are described in patent application PCT/EP95/03814. The process comprises the features that
a) the brown coal is subjected to a mechanically applied initial surface pressure which is below the maximum surface pressure occurring in the process and at which thermal energy is supplied to the brown coal by steam which heats the brown coal, with condensation, PA1 b) and then, without further supply of steam, the surface pressure is increased to at least 2.0 MPa to such an extent that the water present in the heated brown coal is expressed or squeezed out, PA1 c) the brown coal being preheated by waste heat, prior to the supply of steam, and the waste-heat source used being hot water expressed from the brown coal from an earlier pass in the process. PA1 in which brown coal is thermally dewatered by introducing superheated steam into the brown coal contained in an autoclave in a pressurized atmosphere of approximately 3.0 MPa.
The considerable engineering and energetic advantages produced in this process are described in the said patent application in which, in addition, the fundamental form of two apparatuses for carrying out the above-described process is dealt with, that is to say a double-belt press for receiving brown coal distributed flat in bed form, and a platen press which has a press ram and press base and which receives the brown coal distributed flat in bed form.
The journal "Braunkohle 39 (1987) issue 4, pages 78 to 87" describes another process for dewatering brown coal, the so-called "Flei.beta.ner process",
The brown coal heated by this means, after emptying the autoclave, is transferred to a dry coal bunker, where the thermally dewatered brown coal is cooled by post-ventilation and thus post-dried. In conjunction with this process, during emptying of the autoclave, hot water contained therein is conducted away separately as waste water and fed to an adjacent autoclave to heat the cold brown coal contained therein.